U.S. patent application number 17/008266 was filed with the patent office on 2020-12-24 for voltage threshold sensing systems and related methods.
This patent application is currently assigned to SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. The applicant listed for this patent is SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. Invention is credited to Pavel Londak, Alexandra-Oana Petroianu, Catalin Ionut Petroianu.
Application Number | 20200400726 17/008266 |
Document ID | / |
Family ID | 1000005062922 |
Filed Date | 2020-12-24 |
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United States Patent
Application |
20200400726 |
Kind Code |
A1 |
Petroianu; Catalin Ionut ;
et al. |
December 24, 2020 |
VOLTAGE THRESHOLD SENSING SYSTEMS AND RELATED METHODS
Abstract
Implementations of voltage sensing systems may include: a high
side current mirror coupled to a reference current source coupled
to at least one diode. The at least one diode may be coupled to a
resistor and to a comparator. The resistor may be coupled to the
ground. The comparator may be coupled with a reference voltage. The
comparator may be configured to receive a comparison voltage from
the diode and output whether the comparison voltage is higher or
lower than the reference voltage.
Inventors: |
Petroianu; Catalin Ionut;
(Bucharest, RO) ; Petroianu; Alexandra-Oana;
(Bucharest, RO) ; Londak; Pavel; (Hutisko Solanec,
CZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC |
Phoenix |
AZ |
US |
|
|
Assignee: |
SEMICONDUCTOR COMPONENTS
INDUSTRIES, LLC
Phoenix
AZ
|
Family ID: |
1000005062922 |
Appl. No.: |
17/008266 |
Filed: |
August 31, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15961698 |
Apr 24, 2018 |
10761119 |
|
|
17008266 |
|
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62546701 |
Aug 17, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 19/16523 20130101;
G01R 19/16519 20130101; G01R 19/16576 20130101 |
International
Class: |
G01R 19/165 20060101
G01R019/165 |
Claims
1. A voltage sensing system comprising: a high side current mirror
coupled to a reference current source coupled to a Zener diode, the
Zener diode coupled to a resistor and to a comparator; wherein the
resistor is coupled to ground; and wherein the comparator is
coupled with a reference voltage and configured to receive a
comparison voltage from the Zener diode and to output whether the
comparison voltage is higher or lower than the reference
voltage.
2. The system of claim 1, wherein the current mirror further
comprises two p-channel metal-oxide-semiconductor field-effect
(PMOS) transistors coupled together.
3. The system of claim 2, wherein a gate of each of the two PMOS
transistors are coupled to a drain of one of the two PMOS
transistors.
4. The system of claim 1, further comprising a second comparator
coupled with a second reference voltage and configured to receive a
second comparison voltage from the Zener diode and output whether
the comparison voltage is higher or lower than the reference
voltage.
5. The system of claim 1, further comprising a second resistor
coupled between the current mirror and the comparator.
6. A voltage threshold sensing system comprising: two p-channel
metal-oxide-semiconductor field-effect (PMOS) transistors coupled
together, gates of the two PMOS transistors coupled to a drain of a
first one of the two PMOS transistors, the drain of the first one
of the two PMOS transistors coupled with a first constant current
source, and a drain of a second one of the two PMOS transistors
coupled to a diode; and two n-channel metal-oxide-semiconductor
field-effect (NMOS) transistors coupled together, gates of the two
NMOS transistors coupled to the drain of a first one of the two
NMOS transistors, the drain of the first one of the two NMOS
transistors coupled with a second constant current source, and a
drain of a second one of the two NMOS transistors coupled to the
diode; wherein the diode is coupled with an input of a comparator;
and wherein the comparator is configured to determine whether a
supply voltage coupled to the first two PMOS transistors is above
or below a reference voltage coupled to another input of the
comparator.
7. The system of claim 6, wherein the diode is a Zener diode.
8. The system of claim 6, further comprising a second comparator
coupled with a second reference voltage and configured to receive a
second comparison voltage from the diode and output whether the
comparison voltage is higher or lower than the reference
voltage.
9. The system of claim 6, further comprising a fifth transistor
coupled between one of the two NMOS transistors and the
comparator.
10. The system of claim 9, wherein the fifth transistor is an NMOS
transistor.
11. A voltage threshold sensing system comprising: two p-channel
metal-oxide-semiconductor field-effect (PMOS) transistors coupled
together, the two PMOS transistors coupled with a first constant
current source and with a diode; and two n-channel
metal-oxide-semiconductor field-effect (NMOS) transistors coupled
together, the two NMOS transistors coupled with a second constant
current source and with the diode; wherein the diode is coupled
with an input of a comparator; and wherein the comparator is
configured to determine whether a supply voltage coupled to the
first two PMOS transistors is above or below a reference voltage
coupled to another input of the comparator.
12. The system of claim 11, wherein a drain of a first one of the
two PMOS transistors is coupled with the first constant current
source.
13. The system of claim 11, wherein a drain of a first one of the
two NMOS transistors is coupled with the second constant current
source.
14. The system of claim 11, wherein a drain of a second one of the
two PMOS transistors is coupled to the diode.
15. The system of claim 11, wherein a drain of a second one of the
two NMOS transistors is coupled to the diode.
16. The system of claim 11, wherein gates of the two PMOS
transistors are coupled to a drain of a first one of the two PMOS
transistors.
17. The system of claim 11, wherein gates of the two NMOS
transistors are coupled to a drain of a first one of the two NMOS
transistors.
18. The system of claim 11, wherein the diode is a Zener diode.
19. The system of claim 11, further comprising a second comparator
coupled with a second reference voltage and configured to receive a
second comparison voltage from the diode and output whether the
comparison voltage is higher or lower than the reference
voltage.
20. The system of claim 11, further comprising an NMOS transistor
coupled between a source of one of the two NMOS transistors and the
comparator.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This document claims the benefit of the filing date of U.S.
Provisional Patent Application 62/546,701, entitled "Voltage
Threshold Sensing System and Related Methods" to Catalin-Ionut
Petroianu et al. which was filed on Aug. 17, 2017, the disclosure
of which is hereby incorporated entirely herein by reference.
[0002] This document is also a continuation of U.S. patent
application Ser. No. 15/961,698, entitled "Voltage Threshold
Sensing Systems and Related Methods," to Petroianu et al., which
was filed on Apr. 24, 2018, now pending, the disclosure of which is
hereby incorporated entirely herein by reference.
BACKGROUND
1. Technical Field
[0003] Aspects of this document relate generally to systems and
methods for determining whether an input voltage is above, below,
or equal to a reference voltage value.
2. Background
[0004] Generally, to compare a higher valued voltage with a lower
reference voltage used as a voltage threshold, the higher voltage
is divided with a resistive divider and uses a comparator that
compares the now divided voltage with a lower reference
voltage.
SUMMARY
[0005] Implementations of voltage sensing systems may include: a
high side current mirror coupled to a reference current source
coupled to at least one diode. The at least one diode may be
coupled to a resistor and to a comparator. The resistor may be
coupled to the ground. The comparator may be coupled with a
reference voltage. The comparator may be configured to receive a
comparison voltage from the diode and output whether the comparison
voltage is higher or lower than the reference voltage.
[0006] Implementations of voltage sensing systems may include one,
all, or any of the following:
[0007] The at least one diode may be a Zener diode.
[0008] The current mirror may further include two p-channel metal
oxide semiconductor field effect (PMOS) transistors coupled
together.
[0009] A gate of each of the two PMOS transistors may be coupled to
a drain of one of the two PMOS transistors.
[0010] The system may further include a second comparator coupled
with a second reference voltage and configured to receive a second
comparison voltage from the diode and output whether the comparison
voltage is one of higher and lower than the reference voltage.
[0011] The system may further include a second resistor coupled
between the current mirror and the comparator.
[0012] Implementations of voltage sensing systems may include: a
first high side current mirror including a first transistor and a
second transistor. The first high side current mirror may be
coupled to a first reference current. The system may include a
second high side current mirror comprising a third transistor and a
fourth transistor. The second high side current mirror may be
coupled to a second reference current. The system may include at
least one diode coupled between the first high side current mirror
and the second high side current mirror. The at least one diode may
be coupled to a comparator. The first high side current, the second
high side current, and the at least one diode may be coupled to
ground. A current passed by the second transistor may be greater
than a current passed by the fourth transistor. The comparator may
be coupled with a reference voltage and configured to receive a
comparison voltage from the diode and output where the comparison
voltage is higher or lower than the reference voltage.
[0013] Implementations of voltage sensing systems may include one,
all, or any of the following:
[0014] The system may further include a fifth transistor coupled
between the second high side current mirror and the comparator.
[0015] The fifth transistor may be an n-channel
metal-oxide-semiconductor field-effect (NMOS) transistor.
[0016] The at least one diode may be a Zener diode.
[0017] A gate of the first transistor and a gate of the second
transistor may be coupled to a drain of the first transistor or the
second transistor.
[0018] A gate of the third transistor and a gate of the fourth
transistor may be coupled to a drain of the third transistor or the
fourth transistor.
[0019] The first current mirror and the second current mirror may
further include two PMOS transistors coupled together.
[0020] The gate of the fifth transistor may be coupled to the
output of the fifth transistor.
[0021] Implementations of voltage sensing systems may include: two
p-channel metal-oxide-semiconductor field-effect (PMOS) transistors
coupled together. The gates of the two PMOS transistors may be
coupled to the drain of a first one of the two PMOS transistors.
The drain of the first one of the two PMOS transistors may be
coupled with a constant current source. A drain of a second one of
the two PMOS transistors may be coupled to a diode. The diode may
be coupled with a high impedance input of a comparator and to a
resistor coupled to ground. The comparator may configured to
determine whether a supply voltage coupled to the second one of the
two PMOS transistors is above or below a reference voltage coupled
to another high impedance input of the comparator.
[0022] Implementations of voltage sensing systems may include one,
all, or any of the following:
[0023] The diode may be a Zener diode.
[0024] The system may further include a second comparator coupled
with a second reference voltage and configured to receive a second
comparison voltage from the diode and output whether the comparison
voltage is higher or lower than the reference voltage.
[0025] The foregoing and other aspects, features, and advantages
will be apparent to those artisans of ordinary skill in the art
from the DESCRIPTION and DRAWINGS, and from the CLAIMS.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Implementations will hereinafter be described in conjunction
with the appended drawings, where like designations denote like
elements, and:
[0027] FIG. 1 is a schematic of a voltage sensing circuit;
[0028] FIG. 2 shows graphs of the rising threshold voltage for a
resistive divider circuit in FIG. 1;
[0029] FIG. 3 is a schematic of an implementation of a voltage
sensing circuit;
[0030] FIG. 4 is a schematic of a system model circuit used for
testing implementations of voltage sensing circuits;
[0031] FIG. 5 is a schematic of an implementation of a voltage
sensing circuit having multiple voltage references and comparators,
one for each of the outputs;
[0032] FIG. 6 is a schematic of an implementation of a voltage
sensing circuit having two current mirrors;
[0033] FIG. 7 are graphs illustrating the transient response of the
circuit of FIG. 3 in the system of FIG. 4 to the rising and falling
of the supply voltage;
[0034] FIG. 8 shows histograms of the supply voltage value when the
Out from the comparator reached 2.8 V when the supply voltage was
rising for the circuit in FIG. 3;
[0035] FIG. 9 is a corresponding histogram of FIG. 8 of the supply
voltage value when the supply voltage was falling;
[0036] FIG. 10 is a histogram of the rising threshold voltage of an
implementation of a voltage sensing circuit done using actual
silicon chips at room temperature of 27.degree. C.; and
[0037] FIG. 11 is a histogram of the falling threshold voltage of
an implementation of a voltage sensing circuit using actual silicon
chips at room temperature of 27.degree. C. corresponding with the
histogram in FIG. 10.
DESCRIPTION
[0038] This disclosure, its aspects and implementations, are not
limited to the specific components, assembly procedures or method
elements disclosed herein. Many additional components, assembly
procedures and/or method elements known in the art consistent with
the intended voltage sensing systems will become apparent for use
with particular implementations from this disclosure. Accordingly,
for example, although particular implementations are disclosed,
such implementations and implementing components may comprise any
shape, size, style, type, model, version, measurement,
concentration, material, quantity, method element, step, and/or the
like as is known in the art for such voltage sensing systems, and
implementing components and methods, consistent with the intended
operation and methods.
[0039] Referring to FIG. 1, a system 2 for comparing (sensing) a
higher valued voltage with a lower valued reference voltage used as
a voltage threshold is illustrated. As illustrated, the circuit of
system 2 divides the higher voltage with a resistive divider and
uses a comparator that compares the now divided voltage with a
lower reference voltage. As illustrated in FIG. 1, where the supply
voltage 4 has a higher potential (value) than the reference voltage
V.sub.reg 6, in order to permit accurate comparison, the voltage is
divided between two resistors 8 and fed into a comparator 10. The
comparator circuit 10 then outputs 12 the appropriate signal (or no
signal) depending upon how the comparator circuit 10 is designed if
the input voltage 4 is higher or lower than the reference voltage
V.sub.reg 6.
[0040] This resistive divider system 2, implemented using those
standard resistor designs and types in a complementary metal oxide
semiconductor (CMOS) process technology, may exhibit any of the
following: large area size for the system when current consumption
by the system needs to be low; high current consumption when the
system area size needs to be low; internal variations of the
reference voltage and/or offset of the comparator (due to process
corners and/or device mismatch) may be multiplied by the gain of
the resistive divider resulting in a higher variability in the
voltage threshold detection of the system. Compensating for these
issues may translate into requiring use of complex internal circuit
blocks which can increase the current consumption of the
conventional system and/or increase the die size. Furthermore, to
be able to sense whether the voltage is over or under the threshold
voltage to a defined level of accuracy, some form of trimming via
fuses, etc. is necessary with systems such as these to compensate
for process and component variations in the system. Finally, the
resistive voltage divider will consume at least some current; the
current consumption of the system will increase as the sensed input
voltage increases.
[0041] For systems like those in system 2, the effect of
temperature on system operation may further act to impede the
accuracy of the system. For the system 2 illustrated in FIG. 1, all
variations from the internal circuit component blocks (variations
in the voltage reference, the offset of the comparator, etc.) are
multiplied by the gain of the resistive divider, where the gain is
defined as gain=(R2+R1)/R2, at each temperature. Referring to FIG.
2, graphs of the rising threshold voltage for a resistive divider
circuit 2 placed in the system model illustrated in FIG. 4 and the
performance tested using a Monte Carlo simulation using 300 runs at
each temperature are illustrated. The use of the Monte Carlo
simulation was done to simulate the effects of process technology
variations in the components of the system and temperature
variations of the system itself. The resistor sizing was adjusted
so that the results of the experiment would produce rising voltage
threshold values similar to those disclosed by the system
illustrated in FIG. 4, which will be discussed later in this
document while keeping all the internal components of the system
the same (voltage reference value, comparator, etc.).
[0042] By inspection of the graphs, the resistive divider results
in high voltage variation across temperatures (comparing the mean
values across temperature) and across processes (comparing the
standard deviations of each histogram at each temperature).
TABLE-US-00001 TABLE 1 UL = LL = Mean + Mean - (UL-Mean)/
(LL-Mean)/ Temp Mean Std. Dev. 6*(Std. Dev.) 6*(Std. Dev.) Mean
Mean [.degree. C.] [V] [V] [V] [V] [%] [%] -10 5.536 2.22E-01 6.870
4.202 24.1% -24.1% 27 5.290 2.15E-01 6.582 3.997 24.4% -24.4% 85
4.872 2.05E-01 6.101 3.643 25.2% -25.2%
[0043] Table 1 shows the summary data output values from the Monte
Carlo simulation for the resistive divider system 2 shown in FIG.
1. The simulation was carried out at -10.degree. C., 27.degree. C.,
and 85.degree. C. with a desired threshold voltage set at 5.3 V.
The temperature range was designed to include the operating
temperature range for consumer electronics of between 0.degree. C.
to 70.degree. C. However, were the temperature range of the
simulations done to include the automotive standard (extended
range) of -40.degree. C. to 125.degree. C., the observed variation
in outputs from the system would be higher than those disclosed in
these experiments. The supply voltage for the experiment varied
from 0 V to about 40 V and was ramped during each subsequent Monte
Carlo run by 30 mV per microsecond from 0 V to about 40 V to create
rising threshold value observations (observations taken as the
supply voltage is rising rather than falling). While these values
were selected for the purposes of conducting the simulation, the
performance of actual threshold voltage sensing systems is not a
function of the particular threshold voltage or voltage ramping
rates/slopes. The implementations are designed to sense movement in
the supply voltage using any voltage ramping rate/slope and supply
voltage according to the design of the circuit for specific
applications. As can be observed by inspecting the values in Table
1, the average threshold voltage detectable by the system varied
significantly across temperature and also across the process window
itself [see the 24+% upper limit (UL) and lower limit (LL) values
in Table 1]. If the specification for threshold voltage variation
is 2% at 27.degree. C. temperature and 5% across all temperatures
from -10.degree. C. to 85.degree. C., the resistive divider does
not produce results meeting that standard based on the Monte Carlo
simulation results.
[0044] Referring to FIG. 3, a circuit diagram of an implementation
of a threshold voltage sensing circuit 14 is illustrated. As
illustrated, the section 16 of the circuit in dotted lines is the
portion that differs in structure from the resistive divider
circuit system 2 illustrated in FIG. 1, and this portion of the
circuit processes the supply voltage 18 to generate the comparison
voltage fed into the comparator 20 for use in comparing with the
reference voltage V.sub.reg 22. The circuit 14 of FIG. 3 uses a
high side current source in series with a Zener diode 24 and a
resistor 26 to create a comparison voltage from the supply voltage
18.
[0045] Described another way, FIG. 3 illustrates a high side
current mirror 28 coupled to a reference current source 30. The
high side current mirror 28 and reference current source 30 are
coupled to at least one diode 24. In other implementations, more
diodes may be used. The diode may be a Zener diode in various
implementations. As illustrated, the at least one diode 24 is
coupled to a resistor 26 and to a comparator 20. The comparator 20
is coupled with a reference voltage 22 and the comparator 20 is
configured to receive a comparison voltage from the diode 24 and
output whether the comparison voltage is higher or lower than the
reference voltage.
[0046] In specific implementations, to detect a desired threshold
of an increasing/decreasing input supply voltage, the circuit
includes the following: a PMOS current mirror 28 (M1 and M2) which
act to copy a reference current from a reference current source 30
(I.sub.ref) to output to a Zener diode (D.sub.z) 24, a resistor
(R1) 26 to produce a comparison voltage (comp). The comparison
voltage is then input to the comparator 20 along with the voltage
reference 22 to produce the comparator output. The PMOS transistors
M1, M2 that form the current mirror have their sources connected
together to the sensed input voltage. The gates of the PMOS
transistors M1, M2 are also connected together to the drain of the
first PMOS transistor M1, and the second PMOS transistor M2's drain
forms the current mirror output. The Zener diode D.sub.z has its
cathode connected to the output of the current mirror (from
transistor M2) and its anode connected to the first terminal of the
resistor R2 and also to one of the inputs of the comparator (which
may be a high impedance input in various implementations). Which
high impedance input of the comparator the anode is coupled with
depends on the output polarity desired [whether logic/output signal
high (1) or logic low (0) is desired when the comparison voltage
exceeds a certain level]. As illustrated, the other high impedance
input of the comparator is connected to a voltage reference
V.sub.ref. The other terminal of the resistor R1 is connected to
ground.
[0047] Because of the structure of this circuit, implementations of
the system are able to more accurately detect input voltage
thresholds higher than the Zener diode's breakdown voltage plus the
reference voltage. The circuit design has the property that, when
the input supply voltage is lower than the Zener breakdown voltage,
the output current from the PMOS current mirror is null
(substantially zero). This function of the circuit works to ensure
that the circuit has a low quiescent current when the input supply
voltage is below the Zener diode breakdown voltage. Because of this
ability of the circuit to ensure low quiescent current, in various
implementations there may be no need for including an induced sleep
mode function for the overall system/device to prevent current
draw. Furthermore, when the input supply voltage is higher than the
Zener diode breakdown voltage but lower than the desired threshold
voltage, the output current of the current mirror begins
increasing. Because the output of the current mirror, the Zener
diode, and the resistor R1 are in series and since the inputs of
the comparator in various implementations may be high impedance in
particular implementations, the currents through each portion of
the circuit may remain substantially the same, permitting the
voltage over the resistor to mimic any rising/falling slope of the
input supply voltage shifted by the Zener diode breakdown voltage.
When the input supply voltage is higher than the sum of the Zener
diode breakdown voltage and the reference voltage, the voltage on
the resistor may mimic any rising/falling of the input supply
voltage (shifted by the Zener breakdown voltage) until the output
current of the current mirror reaches a maximum value determined by
the ratio of the reference current and the current mirror. This
behavior limits the total current consumption of the circuit in
spite of continuing increases in the input supply voltage.
[0048] When the input supply voltage is equal to the sum of the
Zener breakdown voltage and the reference voltage, the comparator
outputs its output signal (a 0 or a 1, or other signal depending on
the structure of the particular comparator being used and whether
an inverter is also present). This output signal may be any output
from any of a wide variety of comparators. The output signal may be
used in a wide variety of applications where detection of a voltage
level relative to a threshold voltage is needed, including, by
non-limiting example, battery charging, sensor signaling,
electrical switching applications, fault detection, and many
others.
[0049] Although the above implementation utilizes Zener diodes in
breakdown mode to shift the input voltage to a lower voltage level
closer to the voltage reference level while maintaining the same
voltage behavior in time, other types of diodes may be used to
create similar effects. By non-limiting example, in various
implementations, two or more forward biased diodes in series may be
employed rather than a Zener diode operating in breakdown mode.
Other diode types arranged in various configurations configured to
produce the same or similar effect as the Zener diode may also be
employed in various implementations.
[0050] In implementations of voltage sensing circuits like those
disclosed herein, the offset of the comparator and other internal
non-idealities translate directly (1:1) into observed variation of
the sensed threshold voltage (the comparison voltage). This
contrasts with the performance of the resistive divider system 2
previously discussed where the effect of the non-idealities are
multiplied by the gain of the divider. Because of this, threshold
voltage sensing circuits like those disclosed herein may
demonstrate more stable performance over variations of the supply
voltage and variations of temperature than the resistive divider
system 2. Furthermore, implementations of voltage sensing circuits
like those disclosed herein may have much lower area when
physically implemented when compared with resistive divider circuit
systems 2, particularly where low quiescent currents from the
device are specified. Also, the accuracy of sensing the movement of
the supply voltage away from or toward a threshold voltage may be
improved without using any form of trimming.
[0051] Referring to FIG. 4, a schematic of a circuit used to
perform Monte Carlo simulations of the circuit 14 illustrated in
FIG. 3 is illustrated. The circuit 14 of FIG. 3 was placed in the
box 32 in the center of the figure with the supply voltage entering
and vss leaving along with out1 and out2 (multiple outputs). Out1
is an open drain output with a 625 ohm external resistor connected
to the supply voltage pin of the circuit. The same temperature
ranges and rising and falling voltage ranges were then applied to
the circuit during 300 Monte Carlo runs conducted at each
temperature (-10.degree. C., 27.degree. C., 85.degree. C.).
[0052] Referring to FIG. 5, another implementation of a threshold
voltage sensing system 44 is illustrated. As illustrated, the
smaller section 46 of the circuit in dotted lines is the portion
that differs from the resistive divider circuit 2 in FIG. 1, and
this portion of the circuit processes the supply voltage to
generate the comparison voltage. In this implementation, a version
of the circuit designed to provide a comparison voltage to multiple
comparators 48 is illustrated. As illustrated, multiple comparators
48 can have one input coupled with the comparison voltage output of
the threshold voltage sensing circuit and a second input coupled to
various reference voltage. In such implementations, the outputs of
each of the multiple comparators can vary from each other in logic
levels (0, 1, etc.) depending on the value of the comparison
voltage and the value of the particular reference voltage used by
each comparator. In various implementations disclosed in this
document, the comparators may be open-drain or push-pull. As
illustrated, n comparators may be coupled to the comparison voltage
output of the threshold voltage circuit, connected to n reference
voltages and producing n outputs from the system. The various n
references voltages may be the same value, all different values, or
various combinations of the same and different values in various
implementations. Also, the supply voltage may be an alternating
current (AC) voltage source in various implementations.
[0053] Referring to FIG. 6, another implementation of a threshold
voltage sensing system 50 is illustrated. The system includes a
first high side current mirror 52 and a second low side current
mirror 54. The first high side current mirror 52 includes a first
transistor 56 and a second transistor 58. The first high side
current mirror 52 is coupled to a first reference current 60. The
second low side current mirror 54 includes a third transistor 62
and a fourth transistor 64. As can be seen, the second low side
current mirror 54 is coupled to a second reference current 66.
There is one diode 68 coupled between the first high side current
mirror 52 and the second low side current mirror 54. In other
implementations, there may be more than one diode. The diode 68
illustrated is a Zener diode in this implementation, though any of
the other diode implementations disclosed in this document could be
used in place of the Zener diode. The diode 68 is coupled to a
comparator 70. As illustrated, the first high side current, the
second low side current, and the diode are coupled to ground 72.
The comparator is coupled with a reference voltage 74 and is
configured to receive a comparison voltage from the diode 68. The
comparator 70 is configured to output whether the comparison
voltage is one of higher and lower than the reference voltage 74.
In this particular implementation, a current passed by the second
transistor will be greater than a current passed by the fourth
transistor.
[0054] As shown in FIG. 6, this implementation also includes a
fifth transistor 76. The fifth transistor 76 is coupled between the
second low side current mirror 54 and the comparator 70. The gate
of the fifth transistor 76 is coupled to the output of the fifth
transistor. In various implementations, each of the transistors may
include a p-channel metal-oxide-semiconductor field-effect (PMOS)
transistor. As illustrated, a gate of the first transistor 56 and a
gate of the second transistor 58 are coupled to a drain of one of
the first transistor or the second transistor. Likewise, a gate of
the third transistor 62 and a gate of the fourth transistor 64 are
coupled to a drain of one of the third transistor 62 or the fourth
transistor 64.
[0055] The graph in FIG. 7 illustrates the transient response of
the circuit of FIG. 3 in the system of FIG. 4 to the rising and
falling of the supply voltage (SUPPLY external signal). As can be
seen, the comparison voltage (COMP internal signal) remains
substantially constant across the entire period of time the supply
voltage rises and falls. When the out1 signal reached 2.8 V, the
circuit was regarded to have indicated that the comparator had
output a signal based on comparing the comparison voltage and the
reference voltage indicating that the supply voltage had reached
5.3 V. For system implementations with multiple outputs, when the
output OUTn transitions from high to low or from low to high
(depending on the polarity of the signal applied to the input of
the comparator), this acts to signal that the monitoring voltage
has reached a desired value of Vbreakdown_Zener+Vrefn (the nth
reference voltage). By inspection, it is clear that the output
voltage was only present across the range when the supply voltage
reached 5.3 V on the rising side or the falling side, the desired
threshold voltage for this simulation. In the middle of the range,
the out1 signal remained below the trigger amount. By inspection of
FIG. 5, no false triggering of the circuit was observed in response
to the changes in the supply voltage. The slope of the supply
voltage on the rising and falling sides was 30 mV/msec.
[0056] Referring to FIG. 8, histograms of the supply voltage value
when the out1 from the comparator reached 2.8 V for each run in the
Monte Carlo simulations are illustrated when the supply voltage is
rising. The histogram shows the effects of the process and
temperature variation for a desired sensed voltage during a rising
voltage ramp of 5.3 V nominal supply voltage. The rising threshold
in this analysis was defined as the value of the supply voltage
when out1 reached 2.8 V from a high-to-low transition, communicated
by the system as the output of the comparator out1 switching its
logic value. A falling threshold was defined as the value of the
supply voltage when out1 reached 2.8 V from a low-to-high
transition. As can be observed from FIG. 7, the accuracy of the
circuit is +/-1.3% of the typical value of the rising threshold
value which was 5.301 V. Referring to FIG. 9, a corresponding
histogram of the supply voltage value when the supply voltage was
falling is illustrated. Again, as can be observed, the accuracy of
the circuit is +/-1.4% of the typical value of the falling
threshold which is 5.212 V.
[0057] Table 2 shows the results of the simulations for the rising
threshold case while Table 3 shows the results of the simulations
for the falling threshold case.
TABLE-US-00002 TABLE 2 UL = LL = Mean + Mean - (UL-Mean)/
(LL-Mean)/ Temp Mean Std. Dev. 6*(Std. Dev.) 6*(Std. Dev.) Mean
Mean [.degree. C.] [V] [V] [V] [V] [%] [%] -10 5.262 1.15E-02 5.331
5.193 1.3% -1.3% 27 5.301 1.16E-02 5.371 5.232 1.3% -1.3% 85 5.360
1.20E-02 5.432 5.288 1.3% -1.3%
TABLE-US-00003 TABLE 3 UL = LL = Mean + Mean - (UL-Mean)/
(LL-Mean)/ Temp Mean Std. Dev. 6*(Std. Dev.) 6*(Std. Dev.) Mean
Mean [.degree. C.] [V] [V] [V] [V] [%] [%] -10 5.171 1.25E-02 5.246
5.097 1.4% -1.4% 27 5.212 1.24E-02 5.286 5.137 1.4% -1.4% 85 5.268
1.30E-02 5.346 5.190 1.5% -1.5%
[0058] Comparing the variation values in Tables 2 and 3 with those
in Table 1 demonstrates that the circuit implementation of FIG. 3
showed over an order of magnitude reduction in variation during
operation than the resistive divider circuit system 2 of FIG. 1.
This lower variation in voltage achieves the goal of the
implementations of voltage sensing systems as described herein.
[0059] Referring to FIGS. 10 and 11, histograms showing actual
results from implementations of voltage sensing systems in silicon
die are illustrated. The results illustrated in FIGS. 10 and 11 are
from 300 measurements of parts at room temperature of 27 C. The
same number of parts were used in the simulations results shown in
FIGS. 8 and 9 making the results comparable between the simulations
and actual parts. Referring to FIG. 10, the rising threshold
voltage is graphed with a mean of 5.225 V. The data in FIG. 10 is
comparable to the middle graph of FIG. 8 where the rising threshold
in the simulations is charted at 27.degree. C., the mean value is
5.301 V. Referring to FIG. 11, the falling threshold is graphed
with a mean of 5.214 V. The data in FIG. 11 can be compared with
the middle graph in FIG. 9 where the falling threshold in the
simulations is charted at 27 C and the mean value is 5.212 V. These
results indicate that in actual silicon die, the predicted
performance of the voltage sensing systems is comparable to that
predicted in the simulations. Comparing FIGS. 10 and 11 with the
middle histogram in FIG. 2, illustrates proof of concept that
implementations of sensing systems as described herein have a lower
standard deviation across parts than resistor divider devices
illustrated in FIG. 1.
[0060] In places where the description above refers to particular
implementations of voltage sensing systems and implementing
components, sub-components, methods and sub-methods, it should be
readily apparent that a number of modifications may be made without
departing from the spirit thereof and that these implementations,
implementing components, sub-components, methods and sub-methods
may be applied to other voltage sensing systems.
* * * * *